Manage-DHCP
Assigning a New IP Address via DHCP
#resources/networking/dhcp
In Linux, the Dynamic Host Configuration Protocol (DHCP) is responsible for assigning IP addresses automatically on a network. This is typically handled by a background service or daemon called dhcpd.
Why it matters ?
The DHCP server logs which IP addresses are assigned to which devices valuable information in forensic investigations for tracking attackers.
we will Learn how to:
- Manually request a new DHCP-assigned IP without rebooting
- Understand how the
dhcpcdprocess works - Verify your assigned IP using command-line tools
Step-by-Step: Get a New IP from DHCP
Use dhcpcd to Request a New IP
Most Debian-based distros (like Kali Linux) use the dhclient(old version kali) or dhcpcd(new version) utility to interact with DHCP.
dhcpcd --helpsudo dhcpcd eth0
dhcpcd: The DHCP client programeth0: Your network interface (may vary: useip ato list interfaces)
This sends a DHCPDISCOVER request. The DHCP server responds with a DHCPOFFER, and the client confirms it with a DHCPREQUEST.
+------------+ +-----------------+
| DHCP | | Client |
| Server | | (e.g., Kali) |
+------------+ +-----------------+
^ |
| | (1) DHCPDISCOVER
| <---------------------------- |
| |
| | (2) DHCPOFFER
| ----------------------------> |
| |
| | (3) DHCPREQUEST
| <---------------------------- |
| |
| | (4) DHCPACK
| ----------------------------> |
| |
1.DHCPDISCOVER: Client broadcasts a message to find available DHCP servers.
2.DHCPOFFER: Server responds with an available IP address and configuration options.
3.DHCPREQUEST: Client requests the offered IP address.
4.DHCPACK: Server acknowledges and finalizes the IP assignment.